Safety device for elevator



1, 1967 ISAO INUZUKA ET AL 3,333,657

SAFETY DEVICE FOR ELEVATOR Filed Aug. 18, 1966 2 Sheets-Sheet 2 63F U0 MFR 3M0 MSF- 2M0 Z2 Em Sham f//d cur/em Gene/afar Speed of e/el/ofor INVENTORS lsna nvuzazn HIDEO MIYAO 7 ATTORNEY United States Patent 3,333,657 SAFETY DEVICE FOR ELEVATOR Isao Inuzuka and Hideo Miyao, Katsuta-shi, Japan, as-

signors to Hitachi Ltd., Tokyo, Japan, a corporation of Japan Filed Aug. 18, 1966, Ser. No. 573,359 Claims priority, application Japan, Aug. 30, 1965, 40/ 70,700 3 Claims. (Cl. 187-35) This invention relates to safety devices for elevators, and more particularly to an improvement in safety devices for elevators in case of an emergency wherein an elevator is unable to decrease its speed at the upper-most stage or at the lowest stage.

In accordance with the extremely tall buildings now being built, elevators of speeds up to 150 meters per minute have become inetficient, and it is desired that elevators have higher speeds of the order of 300 meters per minute.

One problem accompanying the speed up of elevators, is that of the size of the buffers used in preventing the collision of the elevator when the elevator is unable to decrease its speed at the upper-most stage or at the lowest stage. Namely, buffers must be, in view of safety, of longer buffer stroke as the speed of elevators increase and as a result the vertical passage for elevators must be of longer construction. Such buffers, however, are not economical.

The object of this invention is to provide an improved safety device for an elevator wherein the length of the buffer used in preventing a collision can be of shorter construction even for a high speed elevator.

The details of this invention will be described hereinafter with reference to the annexed drawings.

FIG. 1 shows the construction of an embodiment of a safety device for elevators according to this invention;

FIG. 2 is an electric circuit diagram for the safety device shown in FIG. 1;

FIG. 3 shows curves illustrating speed variations with respect to time of an elevator with the safety device shown in FIG. 1;

FIG. 4 is an electric circuit diagram of another emmodibent of this invention; and

FIG. 5 shows curves illustrating speed variations of an elevator with the safety device as shown in FIG. 4-

The reference symbols in FIGS. 1, 2 and 4 are used to signify the following respectively.

G: Generator in Ward-Leonard system GHF: Series field winding of generator (G) GSF: Shunt field winding of generator (G) GFR: Field rheostat of generator (G) M: Motor in Ward-Leonard system MSF: Shunt field winding of motor (M) MFR: Field rheostat of motor (M) SV: Pulley CA: Elevator cage CW: Counter weight BF: Bulier R: Rope Uzz: Normally open contactor and contact of relay for ascent Da: Normally open contactor and contact of relay for descent 1G0, 2Ga, 3G0, 46a and lMn, 2Ma: Normally open contactor of instructing relay for acceleration and deceleration 3M: Emergency relay for decreasing speed 3Ma: Normally open contactor and contact of 3M UL: Position-detecting contact for initiating slow down operation of speed at the upper-most stage.

DL: Position detecting contact for initiating speed-up operation at the lowest stage GRS: Contact of overs-peed detector 69, 9: Positive and negative terminals of DC. source An elevator cage CA and a counter weight CW are connected by a rope R via a pulley SV, and the pulley is driven by a motor M. The motor M is connected to a generator G by Ward-Leonard connection, and its speed is controlled by adjusting the current flowing through the shunt fiield winding GSF of the generator G. A field rheostat GFR, its resistance value being adjustable by contactors lGa, 2Ga, 3Ga and 4Ga, is provided to adjust the current flowing through the shunt field winding of the generator G. Four contactors Ua, Ua, Da and Da are provided in a bridge connection to reverse the polarity of the motor current so that the direction of rotation of the motor M can be reversed. When the contactor Uzz is closed, the motor M rotates in one direction so that the elevator cage CA ascends, and when the contactor Da is closed, the motor M rotates in the oppoiste direction so that the elevator cage descends.

Further, a controlling operation to weaken the field of motor M is performed for the high speed operation of an elevator. For this purpose, a field rheostat MFR, which is adjustable by contactors lMa and 2Ma, is connected in series with the shunt field winding MSF of the motor M.

In the above construction the motor M is accelerated by subsequently closing the contactors lGa, ZGa, 3Ga and 4Ga at the time when the elevator is started, and is further accelerated up to its full speed by subsequently closing the contactors lMa and 2Ma.

At the time when the speed of the elevator is decreased to cause the elevator to stop, the above contactors are opened in inverse sequence according to the position of the elevator cage, and finally the elevator is stopped by an electromagnetic brake (not shown in the drawings). The variations of the field currents of both the motor M and the generator G together with the variation of the speed of the elevator with respect to time at the time of starting and stopping is shown by the solid line C in FIG. 3.

In case the contactors lGa 4Ga happen to be stuck together or an apparatus to give instructions to decrease the speed fails, the elevator cannot decrease its speed, and the elevator cage CA collides with the buffer BF when the elevator cage CA approaches the uppermost end stage or the lowest end stage. As described above, the stroke of the buffer BF must be of .a longer design in accordance with the increased rated speed of elevators to reduce the shock of collision, and thus it is not economi cal in view of the building cost of the building.

Taking this into consideration the present invention is intended to enable the design of a buffer BF of short stroke, by using a special speed-decreasing device when an elevator approaches any one of its stages, besides the decelerating device used at the intermediate stages between both end stages, whereby the elevator collides with the buffer BF at a speed lower than the rated speed even when the normal decelerating device has failed.

When the elevator cage CA comes to the position opposite the position-detecting contact DL, which initiates a speed-decreasing operation while the elevator cage is descending, the contact DL is closed, whereby the circuit Da-3MDL 6 is completed and the emergency relay 3M for decreasing speed is energized, which is self-held by closing a self-holding contact 3Ma.

Accordingly, since the contactor 3Ma is closed, the field rheostat MFR for the motor M is short circuited, thereby the shunt field winding MSF is connected directly across the terminals 69 and 9 of a DC. power source to strengthen the excitation of the field of the motor M. Accordingly, the speed of the elevator cage CA is decreased more rapidly, as shown by d in FIG. 3, than the normal reduction rate of speed as shown by the curve C in FIG. 3.

Secondly, in case there is a failure in the speed-decreasing device of an elevator, the speed of the elevator is decreased as shown by the characteristic curve b in FIG. 3, whereas in the conventional art, the speed of the elevator is decreased as shown by the characteristic curve a in FIG. 3.

Further, when .the speed of an elevator is accelerated to an abnormally high speed, owing to the load of the elevator and so on, an overspeed detecting contact GRS in FIG. 2 closes, thereby the emergency speed-decreasing relay SM is energized, causing the speed of elevator to decrease in the same manner as described above.

When an elevator cage ascends to the position opposite the position-detecting contact UL arranged at a posit-ion a little short of the upper-most stage, the contact UL is closed, and the emergency decelerating relay SM is energized through the circuit EBUa3M-UL6, and thus the speed of the elevator is decreased in a similar manner as when the elevator is descending.

As described above in detail, since an elevator using the safety device of this invention approaches the uppermost or lowest end stage at a speed lower than the rated speed, and therefore the speed of the elevator cage when it collides the butter BF is low compared to that of an elevator cage wherein the safety device of this invention is not provided, the stroke of buffer BF can be of a shorter design.

FIG. 4 is a connection diagram of another embodiment of this invention, wherein a secondfield rheostat GFR is provided in series with the shunt field winding SGF of generator G, said second field rheostat being able to be short-circuited by the normally closed contactor 3Mb of the emergency decelerating relay 3M, whereby the operation of deceleration in case of an emergency can be performed by weakening the field of the generator G. The variations of the shunt field currents of both the generator and the motor and the variation of the speed of the elevator with respect to time are shown in FIG. 5. The detailed explanations of the curves shown in FIG. 5 are omitted because those characteristics can be easily inferred by an analogy of the explanations of FIG. 3.

What we claim is:

1. A safety device for an elevator driven by a genera- 4 tor-motor set connected in Ward-Leonard system, and running between the upper-most and the lowest end stages of a building, wherein two speed controlling circuits are connected parallel to each other across a common direct current power source EB and 6, namely, (i) a first speed controlling circuit comprising a shunt field winding (GSF) of said generator (G) and a rheostat (GFR) in series with said shunt field winding (GSF), and (ii) a second speed controlling circuit comprising a shunt field winding (MSF) of said motor (M) and a rheostat MFR in series with said shunt field winding (MSF), said first and second speed controlling circuits cooperate to act as a normal decelerating and stopping device for an elevator cage when it approaches one of the intermediate stages and the upper-most and lowest stage, and a third speed controlling circuit, which operates when an elevator cage approaches any one of said both end stages, and which is connected across said direct current power source, said third speed controlling device comprising position-detecting contacts (UL) and (DL), each adapted to detect the approach of the elevator cage to the upper-most stage and to the lowest stage respectively, an overspeed detecting contact (GRS) which detests the speed of an elevator cage when it exceeds a predetermined limited speed and an emergency decelerating relay (3M), said emergency decelerating relay (3M) being connected in series with both of said contacts (UL) and (DL) and said contact (GRS).

2. A safety device for an elevator of claim 1, wherein a normally open contact (3Ma) of said emergency decelerating relay (3M) is connected in parallel to said field rheostat (MFR) of said motor (M).

3. A safety device for an elevator of claim 1, wherein said field rheostat (GFR) of said generator (G) consists of two field rheostats (GFR and (GI- R and a normally closed contact (3Mb) of said emergency decelerating relay (3M) is connected in parallel to said second field rheostat (GFR References Cited UNITED STATES PATENTS 1/1928 Hymans 18'7-35 4/1961 Hesse 187-29 

1. A SAFETY DEVICE FOR AN ELEVATOR DRIVEN BY A GENERATOR-MOTOR SET CONNECTED IN WARD-LEONARD SYSTEM, AND RUNNING BETWEEN THE UPPER-MOST AND THE LOWEST END STAGES OF A BUILDING, WHEREIN TWO SPEED CONTROLLING CIRCUITS ARE CONNECTED PARALLEL TO EACH OTHER ACROSS A COMMON DIRECT CURRENT POWER SOURCE $ AND $, NAMELY, (I) A FIRST SPEED CONTROLLING CIRCUIT COMPRISING A SHUNT FIELD WINDING (GSF) OF SAID GENERATOR (G) AND A RHEOSTAT (GFR) IN SERIES WITH SAID SHUNT FIELD WINDING (GSF), AND (II) A SECOND SPEED CONTROLLING CIRCUIT COMPRISING A SHUNT FIELD WINDING (MSF) OF SAID MOTOR (M) AND A RHEOSTAT MFR IN SERIES WITH SAID SHUNT FIELD WINDING (MSF), SAID FIRST AND SECOND SPEED CONTROLLING CIRCUITS COOPERATE TO ACT AS A NORMAL DECELERATING AND STOPPING DEVICE FOR AN ELEVATOR CAGE WHEN IT APPROACHES ONE OF THE INTERMEDIATE STAGES AND THE UPPER-MOST AND LOWEST STAGE, AND A THIRD SPEED CONTROLLING CIRCUIT, WHICH OPERATES WHEN AN ELEVATOR CAGE APPROACHES ANY ONE OF SAID BOTH END STAGES, AND WHICH IS CONNECTED ACROSS SAID DIRECT CURRENT POWER SOURCE, SAID THIRD SPEED CONTROLLING DEVICE COMPRISING POSITION-DETECTING CONTACTS (UL) AND (DL), EACH ADAPTED TO DETECT THE APPROACH OF THE ELEVATOR CAGE TO THE UPPER-MOST STAGE AND TO THE LOWEST STAGE RESPECTIVELY, AN OVERSPEED DETECTING CONTACT (GRS) WHICH DETECTS THE SPEED OF AN ELEVATOR CAGE WHEN IT EXCEEDS A PREDETERMINED LIMITED SPEED AND AN EMERGENCY DECELERATING RELAY (3M), SAID EMERGENCY DECELERATING RELAY (3M) BEING CONNECTED IN SERIES WITH BOTH OF SAID CONTACTS (UL) AND (DL) AND SAID CONTACT (GRS). 